Alkali metals, those in Group 1 of the periodic table, and alloys of alkali metals, are very reactive in their metallic, or neutral, state. The alkali metals and their alloys are very reactive toward air and moisture and may catch fire spontaneously when exposed to these agents. To avoid the inherent hazards associated with their activity, the neutral metal or alloy must often be stored in vacuo or under an inert liquid such as oil in order to protect it from contact with the atmosphere, which may result in oxidation or other reactions. For example, sodium metal is often stored in Nujol oil which must, to avoid unwanted impurities, be removed prior to use in chemical reactions. This places severe restrictions on its shipment and use.
The combination of alkali metals with silica zeolites, such as ZSM-5, has been extensively studied in many laboratories. For example, it was recently shown that pure silica zeolites can absorb up to 12 mole percent cesium from the vapor phase and comparable amounts of the other alkali metals (except lithium). Prior research with alkali metal encapsulation in all-silica zeolites revealed that such a combination reacts exothermically with water to produce hydrogen quantitatively. (See, for example, “Toward Inorganic Electrides”, A. S. Ichimura, J. L. Dye, M. A. Camblor and L. A. Villaescusa, J. Am. Chem. Soc., 124, 1170–1171 (2002) and “Inorganic Electrides Formed by Alkali Metal Addition to Pure Silica Zeolites”, D. P. Wernette, A. S. Ichimura, S. A. Urbin and J. L. Dye, Chem. Mater. 15, 1441–1448, (2003). The concentration of sodium absorbed by the zeolite compositions, however, was too low to be practical. In addition, the reaction was relatively slow with slow sodium diffusion within the limited zeolite pore size.
The use of potassium metal dispersed on silica as a reagent in organic synthesis has been reported by Levy et al., Angew. Chem. Int. Ed. Engl. 20 (1981) p. 1033. Potassium metal was dispersed onto silica gel (CAS Registry No. 7631-86-9: actually colloidal silica, which has no internal surface area) producing an amorphous material. The reactivity of the material was demonstrated with water and benzophenone, as shown below. See also, Russel, et al., Organometallics 2002, 21, 4113–4128, Scheme 3.
A need exists, therefore, to have alkali metals and their alloys available in a form that may be easily handled without a significant loss in metal reactivity. This invention answers that need.